Before changing coolant it’s a good idea to check the car’s head gasket‘s not gone, allowing exhaust gasses through from the combustion chamber to the engine’s water jacket.
1. Engine off, undo the oil filler cap and check for a creamy deposit indicating water contamination. Can also be due to condensation within the rocker cover so check further.
2. Run engine, undo the cap (careful if hot) and look for bubbling. Don’t confuse this with the water frothing a bit as it is pushed round the system.
3. To make absolutely sure no exhaust gasses are leaking through the head gasket and in to the engine’s cooling system this bit of kit from Frost will give a definite yes or no.
4. With the engine running the rubber pump draws air from the expansion tank up through the test liquid. If any exhaust gasses are present the liquid turns from blue to yellow/ green. Thankfully the Golf left the liquid a nice clear blue.
Now then, you can move on to cooling system. Read "How Do I Flush and Refill my Cooling System?" from our Technical Article.
